Exam 2 Flashcards
How do we define sound?
physical properties and perceptual properties
Physical properties of sound
defines the physical and mathematical properties of sound
perceptual properties of sound
defines the way in which we percieve sounds – based human perception
What is the SHM?
Harmonic– repeating motion
simple– restoring force proportional to displacement
Inertia
resistance of a physical object to any change in its state of motino
potential energy
energy due to position fof teh body or the arrangement of the particles of the system usually associated with restoring forces
kinetic energy
energy due to its motino
velocity
rate of change with discplacement
gravity
force with which all physical bodies attract each other. That thing that gives wright to physical object and causes physical objects to fall toward the group when dropped from a height
cycle
one complete repition
elasticity
the counter force providing movment
newton’s first law of motion
an object at rest will remain at rest unless acted on by an unbalanced force. AN object in motion continues in motion with the same speed and in the same direction unless acted upon by an extrernal forces
hooke’s law
the magnitude of restoring force (elasticity) is proportional to the displacement from rest
How does SHM explain sound?
air is made up of a bunch of molecules each with its own pattern of motion. if an object in that bunch of molecules begins to vibrate as in SHM the air molecules will also vibrate in SHM
Compression
this high pressure region with molecules close together
rarefaction
low- pressure area
What are the two requrements for sound
source and a medim
two requirement that both have the same two features necesssary for sound.
mass and elasticity
Transverse waves
a wave in which the particles of the meduium are displaced in a direction perpendicular to the directon of energy transport
surface waves
a wave in which particles of the medium undego circular motin
longitudinal waves
a wae in which particles of the medium move in a direction parallel to the direction which the wave moves
this type of wave is sound
Waveform
a series of comles waves to look at speech visually, amplitude, frequency, time and variation all of it
What is the range of frequency is relevant for human being
20 hz-20,000hz
what is the spectrum or frequency line spectrum?
we represent the frequency of a wave easily. and amplitude is represented on the y axis and frequency on the x axis
period
the time it took to complete one cycle
how does temperature affect the speed of sound
sound is tranmitted through a medium that has its own pattern of motion. motion depends on temperature so speed of sound varies with temperature
amplitude
sound intensity
displacement
change in position the distance from a reference desceibe both distance and direction
instantaneous amplitude
the magnitude at the point of maximum displacement relative to the magnitude at equilibrium
peak to peak amplitude
the difference in magnitude of displacement between two opposite valence peak points in a wave
Root Mean Square
a statistical measure of the magnitude of varying wave
_______ is the most useful or relates best to listeners perceptions
pressure
Force
force be thought of as any push or pusll applied to an object
pressure
XXXX
reference point for measuring sound and amplitude?
dynes
dynes
a measure of weight (measure the absolute pressre level)
decibel
measure of the relative difference in sound pressure between two sounds
observed pressure
p0
reference sound pressure
pr
two features of the decibel formula that makes it good for measuring sound
logarithmic scale
ration scale
logarithmic scale
reduces the rance of human sensitivity to a manageable scale
ration scale
compares sound pressure to reference value starts the scale at 0 for human
How do we calculate the decibel value of two sounds added together
the pressure in dynes/ cm2 doubles
damping
decrease in amplitude
phase
a measurement of where in the cycle so think about how you can measaure it when around a circle. Measured in degrees, that’s, how you know what degree the phase is
3 main properties of a sound wave
single frequency
pure tones
used for audiometry
intereference
combining waves lead to interference
construction interference
where the combination results in an increase in amplitude
destructive interference
where the combinaton results in a decrease in amplitude
a complex harmonic wave
a nice complex wave
fundamental frequency
lowest frequency
harmonics
higher frequency components that are whole number multiples of the fundamental frequency
a complex wave is periodic
if it is repeating
a fourier series
a complex wave in wich all the frequency components are related
square wave
odd harmonics; sounds harsh
triangle wave
odd harmonics; not as harsh high frequency fall off at a faster rate
sawtooth wave
all harmonics; closest to the vocal source= most relevant to speech because it is the most like speech like the sound our vocal cords make
what is the definition of resonance
resonance is defined as the increase in amplitude that occurs when an object vibrates at is preferred frequency
preferred frequency
the point of vibration in which objects start to resonate
a child on a swing
a child on a swing is essentially a pendulum. The swing will vibrate at a frequency determined by its length. an increase in amplitude is called resonance
mechanical resonance
when an external force is applied to a system vibrated in SHM or at the perfect times, its amplitude increased but its frequency stays the same
acoustic resonance
involves achange in frequency of the otupt more than one resonant frequency
for acoustic resonance what determines the preferred frequency
determined by the physical properties of the structure meaning length
what are the two consequences of acoustic resonance
the sound coming is low and the sound is coming out louder; increase in amplitude the sound that comes back isfiltered
traveling wave
the type of wave that is shown traveling through a medium
standing wave
its the pattern resulting from the presence of two waves (sometimes more) of the same frequency with different direction of travel within the same medium
nodes
are where there is no displacement of the particles (no displacement)
antinodes
are where the displacement is maximum
why do we talk about a tube when talking about acoustic resonance
the sound that resonates will have a wavelength that is proportional to the length of the tube
what is a feature of sound matters for tube resonance
the length– that’s what ‘s changing. besides it’s preferred frequency it will also vibrate a harmonics of its preferred frequency
What happens at a tube’s end? what happens at a tube’s close end?
node at wall of the tube and an antinode at the opening
